1 ltr of paint/ varnish equals approximately 1kg
2ltrs per coat to paint a Phantom (?) 5 coats of paint over the years, theres your 10kg easily!
To be fair thats not that heavy, in 2010 when we weighed all 84 boats at the Stone Nationals there were a couple of plastic boats heavier than that, one considerably!!
Oh, and when do i get my pint, only 1kg out